FIG. 1A illustrates a prior art Point of Sale (POS) system 1000, including a system unit 110 (such as a PC or merely a terminal) and a CRT 120 (which may be integral to the system unit). Consider that the POS system 1000 was originally installed with only two input peripherals, keyboard 130 and bar-code scanner 140. Scanner 140 is mounted in the top of counter 143 underneath scanning window 142 and communicates with the system unit 110 via link 141 (frequently RS-232 or a variant thereof). Keyboard 130 originally communicated directly with system unit 110 via cable 131 (generally using a serial protocol, to be discussed more below). While not shown, the system unit is typically in at least occasional communication with a remote server via wired or wireless technology, e.g., a RS-232 link, telephone line, or Ethernet. Also not shown, the POS system 1000 will typically include a printer for creating customer receipts.
At some point the POS system 1000 of FIG. 1A was expanded through the addition of handheld bar-code scanner 150, which communicates via cable 151. As shown, handheld scanner 150 may be operatively stored on stand 152. The handheld scanner may be added to the POS system 1000 using a device 160 known as a keyboard-wedge and cable 161. When using a keyboard wedge, decoded bar code data is inserted into existing software applications as though the data were entered from the keyboard. Minimal or no changes to the POS software are necessary and an additional interface port on the system unit is not required. This makes it possible to add a handheld scanner to a POS system well after it is initially installed and configured.
FIG. 1B examines how keyboard-wedge based expansion works from a hardware perspective. As previously mentioned, the keyboard 130 communicates to the system unit 110 via a serial protocol. Accordingly, each of these units has a serial port, illustrated in the diagrams by blocks labeled “S”. The serial port is frequently compatible with the RS-232 protocol, or a variation thereof. The serial port is also frequently compatible with the well-known IBM PC-AT keyboard (AT keyboard) serial protocol.
Typical use of mating connectors is symbolically indicated in this and other figures by the use of paired arrow-heads. The arrow head direction indicates the typical plug/receptacle orientation and not the direction of signal flow, which is primarily from the peripherals to the system unit, but in general is bidirectional. Where one of the mating connectors is typically chassis mounted, the tail ends of one of the arrow-heads in the pair will be drawn aligned with the boundary of the box corresponding to the chassis.
An early generation handheld scanner, such as that of the illustrated scanner 150A, generally did not include decoder circuitry within the scanner itself. The decoder circuitry is needed to map the signals detected from scanning the bar code into data directly usable by the software implementing the higher-level POS functionality. The decoder circuitry is represented in the diagrams herein by blocks labeled “D”.
Keyboard-wedge 160 includes block 1610, which includes both decoder circuitry and a serial port, and block 1600, a switch SW. Thus the barcodes scanned by scanner 150A are decoded and then made suitable for serial transmission via block 1610. Not explicitly shown, block 1610 generally outputs a control signal to the switch 1600. The control signal selects which input of the switch is coupled to the output of the keyboard wedge, and hence to the system unit. In particular, when the decoder output is actively sending bar code data, the control signal selects the output of the decoder. When the decoder output is not sending data, the control signal selects the keyboard output.
The switch 1600 and the cabling associated with it have been represented abstractly to facilitate rapid understanding of the higher level architectures of primary interest herein. In particular, the single signal flow lines of most of the drawings are in fact multi-conductor cabling. Functionally, switch 1600 must exhibit the behavior of an electronically controlled double-pole multi-throw switch, providing a separate switched path for each information signal of the chosen serial protocol.
For the case wherein the serial protocol is that of the AT keyboard, cabling makes use of separate conductors for +5VDC power, ground, CLK, and DATA. While the CLK and DATA lines are at times driven by the system unit, the dominant direction for both is from the keyboard. Data is transmitted in a clocked serial variable-data-rate fashion using a single logic zero start bit, 8 data bits (LSB first), a single odd parity bit, and a single logic one stop bit. The clock rate is generally between 10-20 kHz. Common connectors for use with the AT keyboards are the so-called AT style consisting of a 5-pin DIN connector and the newer so-called PS/2 style consisting on a 6-pin mini-DIN connector.
FIG. 1C illustrates a second generation handheld scanner. Here handheld scanner 150B includes not just the scanner head 1500, but the decoder and serial port circuitry 1610 and switch 1600. Essentially, the keyboard wedge has been moved into the handheld scanner. A characteristic of this approach is the use of an expensive wedge-cable 1620 for connection with handheld scanner 150B. At one end, wedge-cable 1620 has Y-shaped features and is sometimes referred to as a “Y-cable.” Wedge-cable 1620 consists for most of its length of what appears outwardly as a single cable. At the scanner-end it may plug into the scanner via a single unified connector. Internally however, wedge-cable 1620 is actually two separate cables: a first cable being the output of switch 1600 and a second cable being the input to the switch 1600 from the output of keyboard 130. These two cables are then broken out separately to form the two arms of the Y and thereby provide connectors for respective cables 161 and 131 to the system unit 110 and the keyboard 130.
FIG. 1D illustrates a third generation handheld scanner in a first mode of operation, compatible with the AT keyboard interface. Here, the bar code scanner being added to the POS system comprises a wireless handheld scanner, represented by block 150C-1; a scanner cradle, represented by block 150C-2; wireless communication path 1700W; and wedge-cable 1620. The scanner includes a scan head 1500, an RF transmit interface 1700X, and battery 1810. The cradle includes an RF receive interface 1700R, decoder and serial port circuitry 1610, switch 1600, and battery charger circuitry 1820.
FIG. 1E illustrates the third generation handheld scanner of FIG. 1D, but in a second mode of operation, compatible with the Universal Serial Bus (USB) interface. Within the cradle 150C-2B, the decoder portion 1340 is shown separately, and a USB interface 1330 is revealed. This system assumes the use of a more contemporary system unit 110, which features an internal USB hub 1320, and a more contemporary keyboard 1300, having an integral USB interface 1310. Since the USB protocol is packet switched, all data from both the scanner and the keyboard are routed via the system unit's internal USB hub 1320. The wedge-cable of FIG. 1D has been replaced by separate USB cables connecting directly to the system unit each of the scanner cradle and the keyboard.
FIG. 1F illustrates a fourth generation handheld scanner. This implementation is motivated and facilitated by the availability and simplicity of low-cost USB-to-wireless adapter 150D-3, which permits the ready addition of a generic wireless interface to the system unit 110 via integral USB hub 1320. Reflecting the evolution of the USB-to-wireless adapter 150D-3, the decoder 1760 is moved into the wireless handheld scanner 150D-1, while the cradle 150D-2 is reduced to comprising just the charger circuitry 1820. Accordingly, the wireless handheld scanner 150D-1 communicates decoded bar code data via wireless link 1740W to USB-to-wireless adapter 150D-3, which passes the data to the USB hub 1320 of system unit 110.
Limitations of the Prior Art
The USB-based handheld scanner solutions described above do nothing for POS systems that have older style RS-232 or AT keyboard based keyboard interfaces. These USB-based solutions also assume that an extra USB port is open for the scanner. This is not always the case, necessitating the additional purchase of an external USB hub.
The above described third-generation handheld scanner, used in AT keyboard compatible mode, makes use of an expensive matched proprietary handheld scanner and cradle and requires an expensive wedge-cable. Because the charging cradle is tethered by the wedge-cable to the system unit, the placement of the charging cradle is restricted to being very close to the system unit.
What is needed is an improved way to add a handheld scanner to existing POS systems that do not have any existing open interface ports suitable for adding new peripherals. What is needed is an improved way to ease installation of a handheld scanner in such systems, lower the cost of the addition, and expand the placement freedom for the charging cradle.